Variable-length quantity: Difference between revisions
add Ada
(add Ada) |
|||
Line 9:
*display these sequences of octets;
*convert these sequences of octets back to numbers, and check that they are equal to original numbers.
=={{header|Ada}}==
<lang Ada>with Ada.Containers.Vectors;
with Ada.Text_IO;
with Ada.Unchecked_Conversion;
procedure VLQ is
package Nat_IO is new Ada.Text_IO.Integer_IO (Natural);
type Byte is mod 2**8;
package Byte_IO is new Ada.Text_IO.Modular_IO (Byte);
type Int7 is mod 2**7;
package Int7_IO is new Ada.Text_IO.Modular_IO (Int7);
type VLQ_Octet is record
Value : Int7 := 0;
Next : Boolean := True;
end record;
pragma Pack (VLQ_Octet);
for VLQ_Octet'Size use 8;
function VLQ_To_Byte is new Ada.Unchecked_Conversion (VLQ_Octet, Byte);
function Byte_To_VLQ is new Ada.Unchecked_Conversion (Byte, VLQ_Octet);
package VLQ_Vectors is new Ada.Containers.Vectors (Natural, VLQ_Octet);
procedure Hex_Print (Position : in VLQ_Vectors.Cursor) is
Value : Byte := VLQ_To_Byte (VLQ_Vectors.Element (Position));
begin
Ada.Text_IO.Put (':');
Byte_IO.Put (Item => Value, Width => 6, Base => 16);
end Hex_Print;
procedure Print (X : VLQ_Vectors.Vector) is
begin
X.Reverse_Iterate (Hex_Print'Access);
Ada.Text_IO.New_Line;
end Print;
function To_VLQ (From : Natural) return VLQ_Vectors.Vector is
Result : VLQ_Vectors.Vector;
Current : Natural := From;
Element : VLQ_Octet;
begin
loop
Element.Value := Int7 (Current mod 2**7);
Result.Prepend (Element);
Current := Current / 2**7;
exit when Current = 0;
end loop;
Element := Result.Last_Element;
Element.Next := False;
VLQ_Vectors.Replace_Element (Result, Result.Last, Element);
return Result;
end To_VLQ;
function To_Int (From : VLQ_Vectors.Vector) return Natural is
use type VLQ_Vectors.Cursor;
Result : Natural := 0;
Iterator : VLQ_Vectors.Cursor := From.First;
begin
while Iterator /= VLQ_Vectors.No_Element loop
Result := Result * 2**7;
Result := Result + Natural(VLQ_Vectors.Element (Iterator).Value);
VLQ_Vectors.Next (Iterator);
end loop;
return Result;
end To_Int;
Test : VLQ_Vectors.Vector;
begin
Test := To_VLQ (16#7f#);
Nat_IO.Put (To_Int (Test), 10, 16); Ada.Text_IO.Put (" = ");
Print (Test);
Test := To_VLQ (16#4000#);
Nat_IO.Put (To_Int (Test), 10, 16); Ada.Text_IO.Put (" = ");
Print (Test);
Test := To_VLQ (16#0#);
Nat_IO.Put (To_Int (Test), 10, 16); Ada.Text_IO.Put (" = ");
Print (Test);
Test := To_VLQ (16#3FFFFE#);
Nat_IO.Put (To_Int (Test), 10, 16); Ada.Text_IO.Put (" = ");
Print (Test);
Test := To_VLQ (16#1FFFFF#);
Nat_IO.Put (To_Int (Test), 10, 16); Ada.Text_IO.Put (" = ");
Print (Test);
Test := To_VLQ (16#200000#);
Nat_IO.Put (To_Int (Test), 10, 16); Ada.Text_IO.Put (" = ");
Print (Test);
end VLQ;</lang>
Output:
<pre> 16#7F# = :16#7F#
16#4000# = : 16#0#:16#80#:16#81#
16#0# = : 16#0#
16#3FFFFE# = :16#7E#:16#FF#:16#FF#:16#81#
16#1FFFFF# = :16#7F#:16#FF#:16#FF#
16#200000# = : 16#0#:16#80#:16#80#:16#81#</pre>
=={{header|C}}==
| |||